#include <stdio.h>
int jumpFloor(int number)
{
	if (number == 1) return 1;
	if (number == 2) return 2;
	else if(number > 2)
		return jumpFloor(number - 1) + jumpFloor(number - 2);
}
int main()
{
	int n;
	scanf_s("%d", &n);
	int result = jumpFloor(n);
	printf("%d", result);
	return 0;
}